The coordinated timing of cell divisions and differentiation between different tissues and between the organism and the environment are critical aspects of normal growth. The control of these processes is important, as cell division irrespective of growth control signals is a hallmark of cancer. Heterochronic genes in C. elegans control the relative timing of cell divisions and differentiation during development. Mutations in these genes result in some cell lineages either omitting or reiterating parts of their developmental program, leading to a variety of abnormal tissues. However, the mutant phenotypes of many of these genes can be suppressed if larvae develop through an alternative pathway called "dauer", chosen in unfavorable conditions. This suggests that some previously characterized heterochronic genes are dispensable for postdauer development, raising the question of what genes control developmental timing in postdauer larvae. The objective of this project is to identify and characterize such genes. Specific Aim 1: To carry out genetic screens to isolate mutants defective in developmental timing postdauer. Specific Aim 2: Genetic analysis of genes isolated in the above screens. Specific Aim 3: To map and clone mutants isolated in the screens.